An air turbine start system includes an air supply duct, an air turbine starter, a starter air valve, a stepper motor, and a controller. The air turbine starter is coupled to the air supply duct to selectively receive a flow of pressurized air therefrom. The starter air valve is mounted on the air supply duct and is movable between a closed position and a plurality of open positions. The stepper motor is coupled to the starter air valve and is configured, in response to valve position commands, to move the starter air valve between the closed position and one or more of the plurality of open positions. The controller is coupled to the stepper motor and is configured to supply the valve position commands to the stepper motor and determine a position of the starter air valve based on the valve position commands supplied to the stepper motor.

An example control component for controlling an engine component includes a housing. The housing defines a cavity configured to receive control circuitry configured to control the engine. The housing includes an exterior layer defining an exterior surface of the housing and an interior polymeric layer defining an interior surface of the housing. The interior polymeric layer is adjacent to and substantially coextensive with the exterior layer. The interior polymeric layer includes an electrically and thermally conductive material. An example technique includes forming the exterior layer and forming the interior polymeric layer.

An example control component for controlling an engine component includes a housing. The housing defines a cavity configured to receive control circuitry configured to control the engine. The housing includes an exterior layer defining an exterior surface of the housing and an interior polymeric layer defining an interior surface of the housing. The interior polymeric layer is adjacent to and substantially coextensive with the exterior layer. The interior polymeric layer includes an electrically and thermally conductive material. An example technique includes forming the exterior layer and forming the interior polymeric layer.

An auxiliary power unit (APU) oil quantity indication system and method provides a stable and accurate oil quantity indication during startup, mission duration and shutdown. The system determines a gulp value at various stages of operation, which is combined with a raw oil quantity indication to provide an indicated oil quantity.

A method of controlling at least part of a start-up or re-light process of a gas turbine engine, the method comprising: determining when a flame in a combustion chamber of a gas turbine engine is extinguished, during a start-up process or re-light process or during operation; purging the combustion chamber by controlling rotation of a low pressure compressor using a first electrical machine, and controlling rotation of a high pressure compressor using a second electrical machine, the combustion chamber downstream of the low pressure compressor and high pressure compressor; and controlling rotation of the low pressure compressor using the first electrical machine, and controlling rotation of the high pressure compressor using the second electrical machine to restart the start-up process or perform the re-light process.

A turbomachine for a vehicle is provided. The turbomachine includes a first rotatable component; a first power source operatively coupled with the first rotatable component; a second power source selectively coupled with the first rotatable component; and a controller having one or more processors and one or more memory devices, the one or more memory devices storing instructions that when executed by the one or more processors cause the one or more processors to perform operations, in performing the operations, the one or more processors are configured to: receive an input indicating an engine shutdown of the turbomachine; and in response to the engine shutdown, cause the second power source to provide power to and rotate the first rotatable component.

A gas turbine engine for an aircraft and a method of operating a gas turbine engine on an aircraft. Embodiments disclosed include a gas turbine engine for an aircraft including: an engine core has a turbine, a compressor, and a core shaft; a fan located upstream of the engine core, the fan has a plurality of fan blades; a nacelle surrounding the engine core and defining a bypass duct and bypass exhaust nozzle; and a gearbox that receives an input from the core shaft and outputs drive to the fan wherein the gas turbine engine is configured such that a jet velocity ratio of a first jet velocity exiting from the bypass exhaust nozzle to a second jet velocity exiting from an exhaust nozzle of the engine core at idle conditions is greater by a factor of 2 or more than the jet velocity ratio at maximum take-off conditions.

A gas turbine engine for an aircraft and a method of operating a gas turbine engine on an aircraft. Embodiments disclosed include a gas turbine engine for an aircraft including: an engine core has a turbine, a compressor, and a core shaft; a fan located upstream of the engine core, the fan has a plurality of fan blades; a nacelle surrounding the engine core and defining a bypass duct and bypass exhaust nozzle; and a gearbox that receives an input from the core shaft and outputs drive to the fan wherein the gas turbine engine is configured such that a jet velocity ratio of a first jet velocity exiting from the bypass exhaust nozzle to a second jet velocity exiting from an exhaust nozzle of the engine core at idle conditions is greater by a factor of 2 or more than the jet velocity ratio at maximum take-off conditions.

The invention relates to a method for monitoring the operating state of an overpressure valve of a turbine engine, the turbine engine comprising a fluid circuit, at least one pressure sensor for the fluid in the fluid circuit, a temperature sensor for the fluid in the fluid circuit, said overpressure valve being configured to limit the maximum fluid pressures in the fluid circuit, and the method comprising the following steps: —(E2) determining an opening or closing indicator of the overpressure valve on the basis of the change in the fluid pressure over time; —(E3) determining an operating state of the valve as a function of a fluid threshold temperature and of the determined opening or closing indicator of the overpressure valve.

An aspect of the present disclosure is directed to a method for mitigating rotor bow in a turbo machine. The method includes rotating a rotor over a first period of time; discontinuing rotation of the rotor for a second period of time; and iterating, over an overall period of time, rotation of the rotor over the first period of time and discontinuing rotation of the rotor for the second period of time.